Person: González Díaz, Germán
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First Name
Germán
Last Name
González Díaz
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Estructura de la Materia, Física Térmica y Electrónica
Area
Electrónica
Identifiers
60 results
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Item Electronic transport properties of Ti-supersaturated Si processed by rapid thermal annealing or pulsed-laser melting(Semiconductor Science and Technology, 2022) Olea Ariza, Javier; González Díaz, Germán; Pastor Pastor, David; García Hemme, Eric; Caudevilla Gutiérrez, Daniel; Algaidy, S; Pérez-Zenteno, F.; Duarte-Cano, S.; García Hernansanz, Rodrigo; Prado Millán, Álvaro Del; San Andrés Serrano, Enrique; Martil De La Plaza, IgnacioIn the scope of supersaturated semiconductors for infrared detectors, we implanted Si samples with Ti at high doses and processed them by rapid thermal annealing (RTA) to recover the crystal quality. Also, for comparative purposes, some samples were processed by pulsed-laser melting. We measured the electronic transport properties at variable temperatures and analyzed the results. The results indicate that, for RTA samples, surface layers with a high Ti concentration have negligible conductivity due to defects. In contrast, the implantation tail region has measurable conductivity due to very high electron mobility. This region shows the activation of a very shallow donor and a deep donor level. While deep levels have been previously reported for Ti in Si, such a shallow level has never been measured, and we suggest that it originates from Ti-Si complexes. Finally, a decoupling effect between the implanted layer and the substrate seems to be present, and a bilayer model is applied to fit the measured properties. The fitted parameters follow the Meyer–Neldel rule. The role of the implantation tails in Si supersaturated with Ti is revealed in this work.Item Ti supersaturated Si by microwave annealing processes(Semiconductor Science and Technology, 2023) Olea Ariza, Javier; González Díaz, Germán; Pastor Pastor, David; García Hemme, Eric; Caudevilla Gutiérrez, Daniel; Algaidy, S.; Perez Zenteno, F.; Duarte Cano, S.; García Hernansanz, Rodrigo; Prado Millán, Álvaro Del; San Andrés Serrano, Enrique; Martil De La Plaza, Ignacio; Lee, Yao-Jen; Hong, Tzu-Chieh; Chao, Tien-ShengMicrowave annealing (MWA) processes were used for the first time to obtain Ti supersaturated Si. High Ti doses were ion implanted on Si substrates and subsequently MWA processed to recrystallize the amorphous layer. The resulting layers were monocrystalline with a high density of defects. Ti depth profiles indicate that diffusion is avoided once recrystallization is produced. Finally, the electronic transport properties measurements point to a decoupling effect between the Si:Ti layer and the substrate. The implanted layer present also a shallow donor and very high Hall mobility.Item Thermal stability of a-SiNx: H films deposited by plasma electron cyclotron resonance(Journal of vacuum science & technology a: Vacuum surfaces and films, 1999) González Díaz, Germán; Martil De La Plaza, Ignacio; Prado Millán, Álvaro DelWe analyze the influence of rapid thermal annealing on Al/SiNx:H/Si structures with a nitrogen to silicon ratio of 1.55 in the insulator bulk. The SiNx:H is deposited by the electron cyclotron resonance plasma method and the films were annealed at temperatures ranging from 300 to 1050 degrees C. We have related the changes of the interface trap density with those of the insulator bulk density of dangling bonds, resistivity, and breakdown field. A sharp dip in the dangling bond density is observed at moderate annealing temperatures, from 1.8 X 10(18) cm(-3) for the as-deposited film down to 9.6 X 10(16) cm(-3) at the point of inversion of the trend between 500 and 600 degrees C. The density of interface states is also reduced in this range of temperatures from 3.6 X 10(11) to 1.2 X 10(11) eV(-1) cm(-2). Resistivity and breakdown held are maintained in the range 5 X 10(14)-5 X 10(15) Ohm cm and 6.4-6.6 MV/cm, respectively, up to a temperature of 600 degrees C. We attribute the improvement of the interface characteristics and the decrease of dangling bonds to a thermal relaxation and reconstruction of the SiNx:H lattice and its interface with the silicon substrate. For temperatures above this threshold the electrical properties suddenly deteriorate and the density of dangling bonds increase. At even higher temperatures (above 900 degrees C) a release of hydrogen from N-H bonds takes place. (C) 1999 American Vacuum Society. [S0734-2101(99)05304-X].Item A robust method to determine the contact resistance using the van der Pauw set up(Measurement, 2017) González Díaz, Germán; Pastor, D.; García Hemme, Eric; Montero, Daniel; García Hernansanz, Rodrigo; Olea Ariza, Javier; Prado Millán, Álvaro Del; San Andrés Serrano, Enrique; Martil De La Plaza, IgnacioThe van der Pauw method to calculate the sheet resistance and the mobility of a semiconductor is a pervasive technique both in the microelectronics industry and in the condensed matter science field. There are hundreds of papers dealing with the influence of the contact size, nonuniformities and other second order effects. In this paper we will develop a simple methodology to evaluate the error produced by finite size contacts, detect the presence of contact resistance, calculate it for each contact, and determine the linear or rectifying behavior of the contact. We will also calculate the errors produced by the use of voltmeters with finite input resistance in relation with the sample sheet resistance.Item Annealing effects on the interface and insulator properties of plasma-deposited Al/SiOxNyHz/Si devices(Semiconductor Science and Technology, 2004) Prado Millán, Álvaro Del; San Andrés Serrano, Enrique; Martil De La Plaza, Ignacio; González Díaz, Germán; Kliefoth, K.; Füssel, W.We have studied and compared the effects of conventional annealing in a forming gas atmosphere (430 degreesC, 20 min) and rapid thermal annealing (RTA) in an inert Ar atmosphere (400-1000 degreesC, 30 s) on Al/SiOxNyHz/Si devices. The samples were deposited by the electron cyclotron resonance plasma method at low temperature (T = 200 degreesC). The devices were characterized by surface photovoltage measurements before applying contacts and by capacitance-voltage measurements. All the as-deposited samples containing N had positive flat-band voltage, which corresponds to negative charge in the insulator and/or in the interface states (Q(INS)). Additionally, trapping of positive charge is observed when measuring from inversion to accumulation after measuring from accumulation to inversion. This behaviour is tentatively attributed to the presence of defects related to N, such as the K centre (N-3=Siup arrow) or the N dangling bond (Si-2=Nup arrow), which may be present in a negatively charged state. For samples of SiO2 composition, with a negligible N content, Q(INS) is positive. High densities of interface states (D-it), above 10(12) eV(-1) cm(-2), are observed in the as-deposited samples. Both the annealing in a forming gas atmosphere and the RTA result in the change of the sign of Q(INS) from negative to positive and a decrease of its absolute value, as well as a decrease of D-it of about one order of magnitude. The trapping of positive charge is also greatly reduced. These improvements of the electrical properties are attributed to the passivation of defects by H present in the forming gas atmosphere or in the SiOxNyHz film itself in a non-bonded state. For RTA temperatures above 700 degreesC the properties of the devices degrade due to the release of H. The combination of RTA and annealing in a forming gas atmosphere results in the best properties.Item A comparative study of anodic tantalum pentoxide and high-pressure sputtered titanium oxide(Journal of Materials Science: Materials in Electronics, 2003) Martil De La Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro Del; San Andrés Serrano, EnriqueIn this work we present a new method to fabricate improved TiO2 films by using a high-pressure sputtering system. In order to minimize the damage induced in the substrate surface by the ion bombardment, a high chamber pressure of 100 Pa is used, which is very much higher than typical values in conventional systems. We present results obtained by Xray diffraction and FTIR spectroscopy. Moreover, we will compare the properties of the resulting TiO2-insulator-metal capacitors with those of anodic Ta2O5. Very thin films of TiO2 have been obtained with a very promising quality for future electron device fabrication.Item Bonding configuration and density of defects of SiOxHy thin films deposited by the electron cyclotron resonance plasma method(Journal of Applied Physics, 2003) Martil De La Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro Del; San Andrés Serrano, EnriqueThe composition, bonding configuration, hydrogen content, and paramagnetic defects of SiOxHy thin films were studied. Films were deposited by the electron cyclotron resonance plasma method at room temperature using SiH4 and O-2 as precursor gases. The film composition was measured by heavy ion elastic recoil detection analysis and energy dispersive x-ray spectroscopy. Suboxide films with compositions ranging from SiO2 to SiH0.38 were obtained. Infrared spectroscopy showed the presence of different Si-O and Si-H vibration modes. The usual estimation of the oxygen to silicon ratio by the wave number of the Si-O-Si stretching band was not accurate for films far from stoichiometry. These off-stoichiometric films also showed a broader Si-O-Si stretching peak than the stoichiometric ones, indicating a higher bonding disorder. The position of the Si-O-Si bending and rocking modes did not depend on the film composition. On the other hand, the peak position of the Si-H modes were found strongly dependent on the Si environment. By single-wavelength ellipsometry at lambda=632.8 nm the refractive index n was found to range between 1.45 (SiO2) and 2.04 (SiO0.06H0.36). Electron spin resonance measurements showed that stoichiometric films presented the well known E' center (.Siequivalent toO(3)) with concentrations in the 10(16)-10(17) cm(-3) range, while for Si-rich films (x<1) the Si dangling bond center (Si-DB, .Siequivalent toSi(3)) was the only detectable defect, with concentrations in the 10(18)-10(19) cm(-3) range. In near-stoichiometric films both E-' and Si-DB centers were found.- Project number: 244
Item Aula Virtual de Electrónica(2021) Prado Millán, Álvaro Del; González Díaz, Germán; Martil De La Plaza, Ignacio; San Andrés Serrano, Enrique; Sánchez Balmaseda, Margarita María; Franco Peláez, Francisco Javier; Olea Ariza, Javier; García Hemme, Eric; Pastor Pastor, David; García Hernansanz, Rodrigo; Caudevilla Gutiérrez, DanielEl proyecto ha consistido en la creación de un espacio virtual en Moodle para publicar contenidos complementarios para las asignaturas relacionadas con el área de la Electrónica. Item Bonding structure and hydrogen content in silicon nitride thin films deposited by the electron cyclotron resonance plasma method(Thin Solid Films, 2004) Martil De La Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro Del; San Andrés Serrano, EnriqueThe bonding structure and hydrogen content of amorphous hydrogenated silicon nitride (a-SiNx:H) thin films have been investigated by infrared spectroscopy and ion beam techniques. Electron cyclotron resonance plasma enhanced chemical vapor deposition was used to produce these films under different values of gas flow ratio, deposition temperature, and microwave power. The amount of bonded hydrogen was calculated from the N-H and Si-H infrared absorption bands. An increase of the SiH4 partial pressure during deposition was found to have the same effect on the H content as an increase of the substrate temperature: both cause a decrease of the N-H bond density and an increase in the number of Si-H bonds. This is explained by a competitive process in the formation of N-H and Si-H bonds during the growth of the film, whereby Si-H bonds are favored at the expense of N-H bonds when either the SiH4 flow or the substrate temperature are increased. Such tendency to chemical order is compared with previous results in which the same behavior was induced by thermal annealing or ion beam bombardment.Item Effect of interlayer trapping and detrapping on the determination of interface state densities on high-k dielectric stacks(Proceedings of the 2009 Spanish Conference on Electron Devices, 2009) Martil De La Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro DelAl/HfO(2)/SiNx:H/n-Si metal-insulator-semiconductor (MIS) capacitors have been studied by electrical characterization. Films of silicon nitride were directly grown on n-type silicon substrates by electron-cyclotron-resonance assisted chemical-vapor-deposition (ECR-CVD). Silicon nitride thickness was varied from 2.96 to 6.64 nm. Afterwards, 12 nm thick hafnium oxide films were deposited by the high-pressure reactive sputtering (HPS) approach. Interface state densities were determined by deep-level transient spectroscopy and simultaneous high and low frequency capacitance-voltage (HLCV). The simultaneous measurements of the high and low frequency capacitance voltage provide interface trap density values in the range of 10(11) cm(2) eV(-1) for all the samples. However, a significant increase of this density of about two orders of magnitude was obtained by DLTS for the thinnest silicon nitride interfacial layers. In this work we probe that this increase is an artifact that must be attributed to traps existing at the HfO(2)/SiN(x):H interlayer interface. These traps are more easily charged or discharged as this interface comes near the substrate, that is, as thinner the SiN(x):H interface layer. The trapping/detrapping mechanisms increase the capacitance transient and, in consequence, the DLTS measurements have contributions not only from the insulator/substrate interface but also from the HfO(2)/SiN(x):H interlayer interface.